The Mind is the Mirror in front of a Mirror that is the Mind

I was asked several questions via the OP - and I will respond here - the answer is neither the body, nor the mind, but rather the absolute Void radiates light externally.

So if you see light internally in your head, that is still the "relative void" and is just the yang qi manifesting. It is a good first sign but the energy has to keep building up to access the Yuan Qi.
When the Yuan Qi is accessed then the body fills with qi and the skull gets soft and pulsates and the fontanelle of the skull opens up - and you enter into immortal breathing.

I was asked if there is anything needed after this - yes the Yuan Qi has to keep building up - this is chapters 7 to 12 or so in the book Taoist Yoga. So the yuan qi has to "crystallize" via the yuan shen - or else the yuan qi will get deconverted back into the post-celestial or mundane state.

It is stated this is difficult since the fuel (the jing) is so close to the fire. So the Qi has to surround the Shen - but if you lift the qi up to the brain to much to check on the power of the shen - this causes a spacetime vortex - as dizziness. So this is described in chapter 11 of Taoist Yoga. I did experience this but I did not understand why it happened. I would describe it as the difference between special relativity and general relativity (but I won't go into details here, lest we stray off topic).

And so that was my "Emptiness" experience - as Taoist Yoga states - when you achieve the first level of enlightenment, the T'ai Chi, you have serenity for a week but there will be great confusion from this.

So when I came out of this spacetime vortex - I knew very clearly that I was neither my mind, nor my body. But what this meant in terms of training - only studying the book in more detail would have given me the answer.

As I have said - people on this website said the book was "too dangerous" and so should not be studied. haha. All I can say is keep studying the book. As I have stated recently - the secret is the "Golden Nectar" has to build up - to build up the golden light from the yang qi - of the jing. And yet this golden nectar as the elixir - the energy is not "material" - in that it is "yin matter" from the future - as this spacetime vortex.

So for example precognition will be experienced more frequently - and longevity as well. But these are just hints.

The ability to change the past and - from the qigong masters I studied with - there are means to exorcise and heal ghosts and to be helped by ancestral spirits - and to see the past and future of locations in space.

But the Yuan Qi as the Emptiness is an eternal process within the Yuan Shen - called the Movement in "non-doing" of the Yuan Shen. So this is also described by other traditions and by science (again I won't go into details right here).
OK I will give one example:

Let this I face the Source and facing the Source is called inquiry, when the I is facing, there is the inquiry. As mirror, in front of the mirror, is reflecting. When you see the mirror? See your face, a reflection. When you keep aside the mirror, where does the reflection go? Back to the face. So this I is inquiring from its own source, which was a reflection in the mind....

This is Poonjaji. Now Westerners commonly claim the Self is the Light - but notice what he states. the Self is the "mirror" whereas the light is just a reflection. His teacher, Ramana Maharshi also states the Self is NOT the light. This is a subtle difference.

So we are taking about a process that is eternal and so the process does not change - we could call this the 5th dimension that is time-like or the Emptiness or the Universe - but it's also called the "three in one unity."

Westerners commonly confuse this with some kind of static oneness that is spatial - I made this error after my first experience - since again I had not studied the philosophy training manual enough, etc. So the complementary opposites remain - the Wuji=the Taiji. The True Yang=undivided yin-yang and the True Yin=undivided yin-yang as well.

I will add that in no way could my experience have been possible without the "empowerment" from http://springforestqigong.com so I encourage people to try getting phone healings or also from his assistant teacher http://guidingqi.com with whom I also studied with privately as well.

So there is the initial "first half" of the training - called the T'ai Chi as enlightenment - but this is just laying the Foundation - but you can fall out of this as well. I "fell out" of enlightenment but because of the empowerment from the teachers - I still have the "ancestral cavity" open - so it is just a matter of continuing the training.